One other question to follow up, when one refers to the growth factors (f1a, f2a, etc.), should they be considered in the metric of log odds. For example, if you had a class that had no probability of AUDY at Y1, would you contstain f1a to be -15 (the threshold limit)?

Thank you, I overlooked the fact that the penn example had continuous indicators. I applied the syntax that you suggested and I get an error message telling me that syntax in the curly brackets (refering to the scale factors) is ignored. I can get the model to run if I do not run a mixture model (that is, if I specify just a binary growth model). I'm using version 2.